page_title: Power dividers and directional couplers
section_title: Wilkinson power divider
hierarchical_section_title: Power dividers and directional couplers / Transmission line types / Power dividers / Wilkinson power divider
caption_attribution_description: Wilkinson power divider constructed from rigid coaxial lines.
context_page_description: Power dividers and directional couplers are passive devices used mostly in the field of radio technology. They couple a defined amount of the electromagnetic power in a transmission line to a port enabling the signal to be used in another circuit. An essential feature of directional couplers is that they only couple power flowing in one direction. Power entering the output port is coupled to the isolated port but not to the coupled port. A directional coupler designed to split power equally between two ports is called a hybrid coupler.
  Directional couplers are most frequently constructed from two coupled transmission lines set close enough together such that energy passing through one is coupled to the other. This technique is favoured at the microwave frequencies where transmission line designs are commonly used to implement many circuit elements. However, lumped component devices are also possible at lower frequencies, such as the audio frequencies encountered in telephony. Also at microwave frequencies, particularly the higher bands, waveguide designs can be used.
context_section_description: The Wilkinson power divider consists of two parallel uncoupled λ/4 transmission lines.  The input is fed to both lines in parallel and the outputs are terminated with twice the system impedance bridged between them.  The design can be realised in planar format but it has a more natural implementation in coax – in planar, the two lines have to be kept apart so that they do not couple but have to be brought together at their outputs so they can be terminated whereas in coax the lines can be run side-by-side relying on the coax outer conductors for screening.  The Wilkinson power divider solves the matching problem of the simple T-junction: it has low VSWR at all ports and high isolation between output ports.  The input and output impedances at each port are designed to be equal to the characteristic impedance of the microwave system.  This is achieved by making the line impedance  of the system impedance – for a 50 Ω system the Wilkinson lines are approximately 70 Ω
caption: Figure 11. Wilkinson divider in coaxial format
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